1. Field of the Invention
This invention relates to photocurable resin compositions and more particularly, to photocurable resin composition which comprises a polymer compound having essentially an active hydrogen-bearing pyrrolidone ring and an amino group, substituted amino group or quaternary ammonium salt, and a bisazide compound as a photocrosslinking agent. The photocurable resin composition of the invention has good dyeability against acid dyes and is thus particularly suitable for use as a material for color filter used in color video cameras and liquid crystal color television sets. The composition is also applicable to the fields of processed parts in the field of electronics and ordinary photoresists such as plate-making materials in the printing industry.
2. Description of the Prior Art
For materials of forming a color filter, there have been widely used photosensitive compositions which comprise natural polymers such as gelatin, glue and the like and a hexavalent chromium compound, used as a photocrosslinking agent, such as ammonium bichromate, potassium bichromate and the like.
In application, such a photosensitive composition is applied onto a substrate such as glass, a solid state image pickup element or the like by a spin coating technique. Subsequently, the coated composition is subjected to ultraviolet exposure through a stripe or mosaic mask and developed to form a colorless transparent pattern on the substrate. This colorless transparent pattern is immersed in a solution containing a dye and dyed. A protective film such as of a resin is formed on the dye pattern. The above procedure is repeated to obtain an intended color filter.
Gelatin or glue is industrially advantageous in that it has god dyeability against acid dyes and good resolving power, and development with water is possible without use of organic solvents. However, since gelatin or glue is a natural polymer, it is difficult to obtain gelatin or glue which has a constant distribution of molecular weight or a constant concentration of amino group necessary for dyeing with acid dyes. Further, such a natural polymer is likely to undergo a so-called dark reaction in which a curing reaction similar to a photo-insolubilizing reaction takes place prior to or after the exposure. Accordingly, the photosensitive solution cannot be preserved over a long term, i.e. it has to be exposed to light and developed within a short time after coating on the substrate. In addition, the use of hexavelent chromium compounds harmful to a human body is also disadvantageous.
In order to overcome these disadvantages, attempts have been made. In such attempts, there has been proposed a photosensitive resin (Japanese Laid-open Patent Application No. Sho 59-48758) which is comprised chiefly of a copolymer of 4,5-methacroyloxychalcone and a tertiary amine having a copolymerizable unsaturated bond. There are also known a photosensitive resin composition (Japanese Laid-open Patent Application No. Sho 58-199342) which comprises as primary components a terpolymer of 2-hydroxyethyl methacrylate, 3-dimethylaminopropyl methacrylate and acrylamide and a diazo compound used as a photocrosslinking agent, and a photosensitive resin composition (Japanese Laid-open Patent Application No. Sho 59-155,412) which comprises a terpolymer of N-vinyl-2-pyrrolidinone, a monomer having a quaternary amine structure and a copolymerizable unsaturated bond, and an alkyl acrylate, and a bisazide compound as a crosslinking agent. Although the chalcone compound-containing composition is advantageous in that it does not use any hexavelent chromium and can suppress the dark reaction, a difficulty is involved from the viewpoint of industrial hygiene and management in that development with aqueous solvents is not possible and thus, organic solvents have to be used for the development.
The chalcone compound is of the type which is dimerized by application of light. In order to obtain a necessary film strength, the ratio of the chalcone groups in the copolymer should increase, with an attendant drawback that it is difficult to balance photosensitivity and dyeability.
The diazo compound-containing system is incomplete with respect to the suppression of the dark reaction and undergoes yellowing of the resin after curing. The composition obtained by adding a bisazide compound to the terpolyer containing N-vinylpyrrolidone has the drawback that it is slightly inferior in dyeability, so that fixation of a dye is very difficult.